1. Field of the Invention
The present invention relates to a technique that controls the driving of a cooling fan used in an electronic apparatus such as a personal computer.
2. Description of the Related Art
In recent years, various types of personal computers, such as notebook computers and desktop computers, have come into wide use in offices and homes. In general, with these types of personal computers, a cooling fan is installed in the neighborhood of a central processing unit (CPU) in order to discharge air, the temperature of which has been elevated due to heat generated by the CPU, to the outside of the casing. Control of the cooling fan is carried out on the basis of temperature data output from a temperature sensor (see, for example, U.S. Pat. No. 6,414,843).
This allows appropriate cooling-fan control that allows for low-noise driving and low power consumption to be implemented (such as rotates the cooling fan only when necessary).
Up to now, the driving of the cooling fan has been controlled by a single controller. The controller receives commands associated with drive control of the cooling fan from software whenever necessary or drives the cooling fan as initialized by software.
With such a system, however, the occurrence of a malfunction or lock-up in the software or a failure in the controller will result in failure to perform the appropriate control of the cooling fan. In this case, as long as the cooling fan continues to rotate there is no problem, but if the cooling fan does not rotate at all, the function of protecting the CPU may not be performed.
With a large business-oriented server computer, it is possible to provide a dual cooling fan system; however, since this system inevitably causes the cost and size to be increased, it is not practical to provide the dual cooling fan system in a personal computer.